user
Explain why some elements have the same properties.
assistant

An element's properties are determined by its atomic structure, which is dependent on the number of protons and neutrons in the nucleus. Elements in the same group, or column, of the periodic table have the same number of protons and electrons, giving them the same elemental properties. For example, all alkali metals (group 1A) have a single valence electron, giving them similar properties such as low densities and high reactivity. This is because all of their atoms have the same number of protons, electrons, and neutrons.